1. Field of the Invention
This invention relates to a process and an apparatus for the sulfonation and sulfation of organic compounds that are liquid at ordinary or reaction temperatures, including such compounds as alcoholic compounds, compounds having sulfonatable double bonds, aromatic hydrocarbons and the like.
The term "sulfonating" as used hereinafter in the specification and claims is sometimes used in a generic sense as applying to both true sulfonation and sulfation, and sometimes in a specific sense to mean true sulfonation. The term "sulfonating" or derivatives thereof is to be construed generically, unless the context in which the term is used requires the specific sense.
More specifically, the present invention relates to an improved process and apparatus for sulfonation wherein the above-mentioned liquid organic compounds are reacted with sulfur trioxide gas diluted with air or other inert gas.
2. Description of the Prior Art
Reactions using concentrated sulfuric acid, fuming sulfuric acid or chlorosulfonic acid as a sulfonation reagent have conventionally been practiced in a liquid-liquid mixture system and most of them are batch processes that use a large amount of the sulfonation reagent. These processes, however, are not free from various disadvantages, such as, the quality of the reaction product varies from batch to batch and/or the reaction product contains a considerable amount of unwanted inorganic compounds.
In recent years, sulfur trioxide (SO.sub.3) has achieved wide use as a sulfonation and sulfation agent. Continuous liquid-gas phase reactions have been attempted and employed on a commercial scale using SO.sub.3. However, the conventional reaction processes using SO.sub.3, such as those mentioned below, entail various problems in production engineering.
For example, a pipe-system reactor, as disclosed in U.S. Pat. No. 2,923,728, Japanese Pat. Publication No. 37407-72, Japanese Pat. Publication No. 8087-73, etc., is suited for limited production rates, but it is not suitable for mass production. In order to obtain a large amount of sulfonated reaction product by the use of a single reaction tube, the diameter of the reaction tube must be made very large. It is difficult, however, to make the diameter of the reaction tube extremely large because it is difficult to achieve adequate cooling (reaction heat removing) that is critically required and for other reasons. When plural reaction tubes are disposed in parallel arrangement, strict control of the liquid-gas ratio is required for each reaction tube and hence this process is not advantageous industrially.
Japanese Pat. Publication No. 37407-72 discloses a process wherein a liquid film of a sulfonatable organic liquid is raised by means of an SO.sub.3 -containing gas. In this proposal, the quantity of the liquid fed in can be increased substantially, in proportion to the square of the diameter of the tube, but the cooling area of the tube wall increases only in direct proportion to the diameter of the tube. Thus, inadequate cooling may occur and this results in an elevated reaction temperature, which in turn causes unacceptable variation of the color of the reaction product. Likewise the thickness of the liquid film essentially increases in proportion to the tube diameter whereby unequal distributions of reactant concentration and temperature are generated inside the liquid film, thereby creating unstable conditions and making it difficult to minimize unwanted side-reactions.